Grinding mill



Sept. 2,1941. c. P. BRASINGTON GRINDING MILL Filed Nov. 2,1938

3 Sheets-Sheet 1 .INVE TOR Ma ATTORNEY;

Sept; 1941- c. P. BRASINGTON 2,254,512

GRINDING MILL Filed Nov. '2, 1938 s sheets-sheet:

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Patented Sept. 2, 1941 UNITED STATES PATENT OFFICE GRINDING MILL Charles P. Brasington, Cincinnati, Ohio Application November 2, 1938, Serial No. 238,385

2 Claims. )(CL 83-12) This invention relates to the art of grinding pigments and powders to a fine state of subdivision. The invention is disclosed particularly in relation to the grinding of paints, printing inks, finishing and cosmetic compositions and the like, and is directed particularly to a new type of grinding mill.

The paint and ink compositions and cosmetic creams, and the like, are ground for the purpose of reducing the size of the particles and also for the purpose of incorporating these particles very thoroughly into the vehicle or other materials with which they are to be associated. Bulk pigment, for example, as well as other substances which require grinding, generally are purchased from the manufacturer of it in somewhat powdery form. This powder is admixed crudely with a vehicle, and the mixture then is ground in a mill of the type to which the invention relates, first, for the purpose of incorporating the powder into the liquid thoroughly and uniformly, and

also for the purpose of subdividing the particles of powder. Some substances are relatively immiscible with the various liquid vehicles; the grinding causes such materials to become wetted by the liquid and facilitates their dispersion throughout the mass of it. Other materials for instance those used in cosmetics tend to be lumpy, and grinding is requisite to obtain the desired creamy consistency,

As a general proposition, the fineness of subdivision of the particles and the intimacy and uniformity with which they are associated with the liquid carrier controls or determines the quality of the final product.

Originally the grinding mills were of the buhrstone type, in which the material was ground between coacting discs or plates. More recently, roller mills have been employed. In these mills the material to be ground is passed between parallel cylindrical rollers that are spaced closely adjacent, or pressed against one another. The rollers of the mills are driven at different speeds, so that the particles passing between the rollers are subjected to a shearing action, as well as to compression. For instance, one of the rollers may be driven at 50 revolutions per minute, the next one cooperating with it at '75 or 100 revolutions per minute and so on. By virtue of the complementary rotation of the rolls, the material being ground is squeezed between the rolls and emerges from the throat as a film; this film is,

conveyed from the throat upon the roller operatingat the higher. speed of the two. The particles thus pass progressively from roll to roll under pressure and shearing action. The machines may include only two rollers, or three, four or five of them, driven at increasing speeds.

The efficiency of a grinding mill, the speed with which it is capable of grinding a given product, and uniformity of the product ground in the machine are dependent largely upon the relative positions of the rolls to one another when other conditions are equal. In the machines of the past, the adjustment of the positions of the rolls has been dependent primarily upon the skill of the operator in charge of the machine. In adjusting the rolls of these machines, it has been requisite for the operator first to make the adjustment in accordance with the nature of the material being ground, and next to adjust the rolls so that they would be parallel with one another, in order that a uniform grinding action across the length of each roll would be attained. For some types of materials it is requisite that the rolls be very close together in order that the material passing between them be subjected to a high pressure. In other cases, where the material is softer and more easily ground and subdivided, a lesser pressure is employed. In either case, it is requisite for uniform grinding that the pressure be uniform throughout the length of the rolls, otherwise the material would be ground differently at opposite sides of the machine.

In the typical roller mills heretofore employed, each roll is adjustably mounted to be movable toward and from the roll adjacent to it, by means of adjusting screws respectively pushing against the roller journals. Each machine has a plurality of these adjusting screws, at least one be provided for each roller journal; these adjusting screws are located on the frame of the machine. It is the usual procedure for an operator to start up the machine and then proceed to adjust the screws controlling each end of each roller, until he has arrived at an adjustment in which the rolls are as parallel with one another as he can make them, and until he has arrived atv an adustment of the pressure between coacting rolls which he thinks suitable for the type of material being ground. If the pressure which the rolls exert against one another is very high, then the rate of grinding is proportionately slow, If the machine is adjusted so that the pressure between the rolls is relatively small, then, of course, a

given mass of the compositions being groundwill pass through the machine relatively rapidly, list correspondingly little grinding being done The primary difliculty with the method. that has been employed in the past has been the dimculty of obtaining appropriate and uniform adjustments of all of the rolls of the machine. It

has been the usual experience to find the first stance, to. illustrate this feature, if each roll is driven at a speed twice as great as the one pre- I as wide as the one preceding it, once the throats dimensions have been predetermined and .the

rolls so set. In other words, the width of each throat is related to the widths of the throats preceding and succeedingit in accordance with little, if any. Under such conditions the grinding.

results are poor, the grinding is slow "and the power consumption of the machineis great 7 At other times it has been found that the rolls are not adjusted into parallel alignment and the pressure along the line of tangential contact varies; the grinding at the one end then is very poor while the grinding at the. other end is a better or worse depending on the relative spacing.

Ordinarily, all of the adjustments aremade by eye alone, throughvisual inspection of the films being carried on therespective. rolls while the machines ,are operated. However, it is relatively impossible even for -the most highly skilledmill operator to discern the difference of half a thousandth of an inch in the thickness between films, yet it is well recognized that a variation of a few ten thousandths of aninch' greatly influences the.

quality offthe grinding. In fact, printing inks rarely are ground in films thicker than a few ten thousandths of an inch at the most.

The objective of thefpresent invention has been to provide grindingmills which require less time to adjust and in which a more uniform grinding action is obtained. The objective has beento provide a grinding mill in which the quality of grinding is not dependent so largely upon the skill of the operator or the accuracy of the adjustments he heretofore has been required to make. Briefly, the present invention is predicated, first, upon the concept of moving the rolls toward and from one another inunison and, next, upon the determination that rapid and uniform grinding action is obtainedif and when there is a the differential speeding of the rolls, regardless of the actual spacing of one roll from another.

In a typical roller mill the first or feed roll is of relatively slow speed, the next roll which cooperates with it is driven at a higher speed, the next-at a stillhigher speed, the next at a'still higher speed, etc. By virtue of the differential speeding, material which is disposed between the first roll and the second, passes through the first throat opening and is conveyedby the roll of becomes congested with material, but, rather,

each set of rolls performs its share of the burden of the grinding operation. The relationship may Film thickness xdifferenflal spoe predetermined and controlled relationship beating rolls become successively smaller as the" material is passed through the mill, while the difierential. speeding between the rolls of the succession is increased.- By virtue of the-simultaneity of movement of the rolls,'a parallel condition between them, once established, is maintained, and thus the time-and the skill necessary to adjust each of the ends of the rolls for-alignment after eachcleaning is avoided. Still more important, the perfection of the alignment of the rolls is predetermined, and is independent of the operators skill. Thisaspect of the. invention is important because of the ease and accuracy with'which the rolls are'brought into cooperating position.

On the other hand, the movement of the rolls is in unison, but at relative rates of adjustment which preferably areproportional or substantially proportional to the differential speeding of.

the m, so that the ratio'between the widths l of the throats between the sets of rolls in in conformity with the relative speeds at which the material is passed through the throats. Formbe expressed mathematically: a

The thickness of the 'filrn passing the first throat 'times the first diflerential speed equals the thickness of the film passing the second 5 film thickness x diiferontial speed, etc.

The principle may be exemplified in a typical three-roll mill as follows:

The first roll is driven, for example, at a relative speed of 50, the next or middle roll at a relative speed of and the last or apron roll at a relative speed of 200. The differential speed between the feed and middle roll is Y50 and between the middle and the apron roll, 100. The diflerential speeding may besaid to be 2 to 1, each roll being driven twice as fast as the one adjacent to it. In such a machine, constructed in accordance with the present invention, the journals of the rolls are so interconnected that the first or feed throat opening is adjusted two units for example, while the second or discharge throat opening is correspondingly adjusted one unit. Thus, if the machine originally be setwith the throats properly proportioned, this condition always will be maintained.

In the preferred machines, the journals of the machines are interconnected for adjustment of the .rolls from a' central point, as for instance, a hand wheel. If the machine is so constructed that the second 'or' middle roll is iournalled in immovable bearings, then both the feed roll and the apron roll are moved toward and away from it in unison. In the preferred'embodiment, each journal of each roll is interconnected with all of the others and, therefore, with the rolls initially the sets of journals at the respective ends of the rolls may be movable in unison independently of me another between the respective ends. In this case, separate control means are provided for the separate sets of journals. For the most part, this construction is not preferred since individual adjustments of the opposite'sides of the rolls are required and it is more diflicult to obtain parallelity between the rolls. Still, this is much more advantageous than adjusting each journal of each roll individually, especially since the relative adjustment of the journals of a set may be predetermined. In the preferred structure all movable journals are interconnected.

The means interconnecting the journals to provide for predetermined relative rates of movement of them upon adjustment of the machine preferably is of welded sheet metal construction and is made as light aspossible to reduce the The frame elements preferably are a weight. moulded of cast iron, in order that they maybe sufliciently strong and rigid to withstand the loads and restrain the vibrations imposed upon them during the grinding operations. If desirous.

' the frame may carry sultable legs and base is is best comprised of adjusting lead screws for i each movable journal. The pitches of the respective adjusting screws are so proportioned as'- The drawings illustrate a preferred embodiment of a three-roll mill of the present invention. From the foregoing description of the principles upon which the machines are built and a from the following description of the. specific details of a typical machine,- it is believed that those skilled in the art Will comprehend the modifications to which the preferred embodiment is susceptible and understand the application of the invention to mills of the four and five-roll type, and likewise to commercial three-roll mills other than the type herein disclosed.

In the drawings,

Figure l is a sectional side elevation of a typical three-roll mill constructed in accordance with the invention. g

Figure '2 is a sectional top plan view showing the assembly of rolls. Figure 2 is taken on the line 2--2 of Figure 1.

Figure 3 is a sectional view showing the interconnecting elements for simultaneous adjustment of the rolls. This view is taken on line 33 of Figure 1. I

Figure 4 is a sectional view taken on the line fi-d of Figure 3 and illustrates the details of an adjusting screw assembly.

Figure 5 is a sectional view taken on the line 5-5 of Figure 4, and illustrates the means for interconnecting adjusting screws on opposite sides of the machine.

Figure 6 is a sectional view taken on the line 66 of Figure 2 and illustrates the journal assembly of the rolls of the machine.

Figure 7 is a fragmentary top plan view of a. grinding roll and journal assembly.

In the drawings, the frame of the mill is indicated generally at I. This frame is comprised of side pieces 2-2, and front and back end plates 3 and 4, respectively. Each side piece of the frame-is comprised of corner post portions 55 at its side edges; these are joined by an integral web portion 6. The front and back end plates include side flanges I which extend inwardly.

The frame is assembled into a rigid structure with the flanges of the end plates being bolted or fixed to the corner posts-5 in a. suitable manner.

The frame of the machine is mounted upon a base, indicated generally at 8, which is comprised of corner posts 9, one for each corner.

then omitted.

The top portions of the respective side P es are cOnflgurated to provide slideways or guides l3, as illustrated in Figure 6, for carrying the journals in which the rolls are mounted. At the front and rear edges these slideways are transversely grooved as at I4, to receive spacer elements i5 which are provided with tenons it for engagement in the grooves. The opposite ends of the spacers l5 likewise are tenoned to receive top guides 11 which are grooved similarly to the lower guides I3. to receive the upper tenons. The upper and lower guideways l1. and 13 are bored and the spacers I 5 are slotted, to receive clamping bolts 18 for holding the upper guides and the spacers rigidly upon the frame. Eachupper slide bar I! comprises an extended portion 19 which is drilled transversely pivotally to receive an adjusting clevis arm 20. The function and details of this structure are described at a later point in the specification.

Lower guides l3 and upper guides ii are constituted to receivethe journal blocks in which the grinding rolls are supported and rotatably mounted. Journal blocks 2i2l are provided for each end journal of the feed roll, journal blocks 22-22 for each end of the middle roll, and journal blocks 23-23 for each end of the apron roll. Each of the blocks is slotted at its lower and upper edges to engage the upper and lower guide bars i3 and II respectively. The sets of journals 2I-2i and 23-23 are free to slide with the rolls. The journals 2222 for the middle roll are keyed, at their upper and lower edges, to the upper and lower rails I3 and I! by the keys mil-24; clamp screws 25 also are passed through the upper rail i! into the blocks t hold these middle blocks in stationary position.

The journal blocks are of split construction; each comprises inner and outer face plates 26 and 21., respectively, as indicated in Figure 2. These plates are counter-bored as at 28-28, and, intermediate the front and rear plates, an antifriction bearing is disposed. The face plates and the anti-friction element of each journal are clamped into rigid assembly by means of the screws 29 which are located at the corners of the block assembly.

The meeting edges of the journal blocks 2! and 22 and the journal blocks 22 and 23 are counterbored to receive seating elements 30 and 3|, respectively, and seating elements 3i and 32, respectively. These elements contain counterbores suited to receive compression springs 33 and 34. The compression springs serve to separate .the ournals of the feed and apron rolls from the middle roll when the pressure against these journals is relieved.

be broken in case an may be water-cooled from theinterior.

'The outer edges of the feed roll and apron roll Journals likewise are bored to receive seats II and 36 and these seats contain apertures suited to receive the breaker plates I1 and II which are included in the adjusting mechanism. The breaker plates-are of conical shape.'and are to obstruction is caught between the rolls,

The grinding rolls of the mill'are preferably ofthe conventional water-cooled type. Each'roll assembly is comprisedof a grinding roll portion 39 which is of hollow construction so that it I The spindles 40 for the rolls are disposed within-the anti-friction bearing elements contained in the respective journals. Each spindle includes a callar portion 4| which passes through a suitable bore in the inner plate of the journal block and a flange portion 42 which is fixedly engaged to the grinding roll. The spindles. are'hollow and each terminates, at the one sided the machine, in a lip ring 43 to whichappropriate connection can be made for the admission of cooling water to the roll. The spindles at this side of the madle for the apron'roll carries a driving gear 49 1 rneamum: I In'the .preferredembodiment of the invention the respectivejournals of the rinding'rolls'are interconnected with one another for relative movement of the mils toward and. from; one.

another in unison. This is done in orderthat there may be maintained apredetermined relationship between'the' throat openingsinter'mediate the respective cooperating pairs of rolls. Whenthe rolls are movedin unison and at pre-.

determined relative rates of movement then any given predetermined relationship between the respective throat openings is maintained irrespective of the actual dimensions of anythroatopen- In of mill as shown'in the drawings thecenter roll is mounted in stationaryjournals and the feed roll is moved toward it and away from it.

construction is employed for thepurpose of aimplicity. The inventionyhowever, contemplates which is in engagement with a driven gear 50 mounted upon the spindle of"the middle roll.

Thespindle of the middle roll also carries a driving gear H which is in engagement with a driven gear 52 -upon .thespindle of the feed roll. Y

In the preferred construction, agear ratio .of.

1 to 2 is maintained between the driving gear I and the driven gear for each of the sets of rolls.

In this instance, therefore, the feed, middle, and

apron rolls operate at a relative speed of 1:2:4,

so that a differential speed of ,1' to 2 between the successive sets of rolls is maintained. This gearing ratio is not requisite or essential; any gearingratio' may be utilized which is suitable for obtaining appropriate shearing action by the rolls upon the particles being ground. For instance, a gear ratiov of 1%} 3 or 4 to 1 may be employed, or, altematively, the gearing ratio between the feed roll and the middle roll may be 1 to 2, for instance, while the ratio between .the middle roll andthe apron roll may be diflers The sprocket gear 45 and the driving and driven ent, e. g. 1 to 3.

machines in which of the rolls are relatively movablein unison or in which any particular roll of the plurality is withheld from movement.

The main adjustment of the rolls is controlled through a hand wheel 62 at-the feed endof the machine or a hand wheel 82:; at the apron end of the'machine. These hand wheels are rigidly mounted upon a rotatable shaft 63, which is carried in journalbrackets 64, and 86. These journals are fastened to the side plateof the machine. Adjacent the center journal 65 a spiral gear 61 is mounted upon the shaft 83 and is keyed to it by means of key 68. A collar 69 is pinned to the shaft intermediate the journalli of the spiral gear, and a collar 10 is pinned to the shaft 83 inwardly of the journal 64 to prevent from being moved longitudinally of its shaft 63 The-webs {of the frame are bored transversely to carrya shaft II. I This shaft extends across the frame of the machine and projects beyond the frame at the side on which the main control shaft is mounted to carry a spindle gear. 12 in meshing engagement withv thespiral gear". The spiral gear I2 is keyed to theshaft "H by the key II and a collar 14 is disposed over the shaft intermediate'the' gear 12 and the face of theweb 'of the frame. A single control wheel may be mounted directly upon. shaft '|l in place of-the front and rear control wheels 62 and no. if desirous. In this case the shaft '63, and

'bracket journals spiral gears i1 and 12 are omitted. V i

At theinner faces of the webs of the frame, at

each side of the machine, aspacing washer I5 is gears 49, 50; 5| and 52 are rigidly mounted upon i V the corresponding-spindles'of the grinding rolls.

The sprocket gear and the driving and driven."

gears are provided with suitable 'collars 53, 54,

55, 56 and 51, respectively. These collars .preferably are integral with the gears or rigidly fixed thereto. The collars are keyed to the respective spindles in the usualmannerqThe spindles which carrylth'e driving anddriven gears, and

the spindle carrying the; sprocket .wheel arev threaded to receive spannernuts 58; 59, 60 and 6|. The structure completes the assembly of the 5 grinding rolls, journals, and driving means for the rolls, upon the frame;

carried by the shaft 1i ,and, inwardly of the spacingwashers, spiral gears 16-16 are keyed to the shaft, one likewise for each side (of the machine, the keys being designated at 11.

The corner posts of the frameare provided with bores extending in a direction parallel to.

the shaft 63 to'receive'adjusting screw assemblies IS-.19 forthe respective journals of ,the

' feed roll and assemblies -80 for the respective journals of the apron roll. The .comer posts at the feed and discharge ends of the mill are bored to receive flanged collars 8I8l and 81-82 respectively. The sets of collars 8| and are i internally threaded. The collars 8i threadedly carry lead screws 8343,; respectively, and the collars 82 'carry the lead screws 84-84 respectively. Each of the shaftsis provided with a sphned or square head, 85 at its interior termithe preferred structure of a three-roll -fulcrum portions 9| the next follows a geometrical progression. For

nal. Spiral gears 86-88 are provided for respective engagement with the spiral gears I8 carried on the shaft 1!. Each of the spiral gears 86 carries collar portions 81-81 on opposite sides of the gear itself, and the collars ar bored and conflgurated to receive the respective squared heads on the lead screws. 19 and 88. The collar portions of the gears 86-88 are engaged in. a pair of supporting bearings 88--88 with one bolted to the side walls of the mill. The lead screws sustain gears 81 in meshing relation with the gears 16, while the spiral gears 86 in turn are effective to rotate the lead screws and permit them to move relatively toward and away from one another as the lead screws are threaded into and out of the nuts 8| and 82.

, Lead screws 'l919 and 8888, respectively, extend beyond the frame of the machine and each engages the clevis arm depending from the extension of the top guideway above it, the

clevis arms being appropriately bored to be disposed over' the shaft. Each of the shafts l8 and 88 also threadedly carries a washer 89 in contact with the clevis arm, and a pair of lock nuts 88.

The portions of the clevis arms 28 adjacent to the washers 89 are configurated to provide which facilitate angular movement of the clevis arms in relation to the axes of the lead screws. The .boresin the. clevises through which the lead screws pass are sufficiently large to permit of angular movement of the fulcrum arms relative to the shafts. The clevis arms are pivoted to the upper rails i! by means of pivots 92. The lug extensions I9 preferably are slotted as shown in Figure 7 and the clevis arms preferably are provided with inwardly extended lug portions 93. The lug extensions 93 are received within the slots of the upper rails and the pivots 92 pass through the upper rail extensions and the lugs on the clevis arms for relative pivotal movement of the arms.

The spacer elements l5 are bored to receive compression pins 94 for engagement with the respective breaker plates 31 and 38, and intermediate the pivots of the clevis arms and the points at which they are connected to the shafts, the arms are bored and threaded to receive adjustable connecting screws engaging the compression pins. The connecting screws for the journals of the feed roll are indicated at 85 and those for the journals of the apron at 98. Each connecting screw carries a head 91 and a lock' nut 98 that is in abutment against the face of the clevis arm.

The relative pitches of the threads of the lead screws engaging the nuts 88 and 8! determine the relative rates of movement of the rolls toward and away from one another. If thepitch of the screw on the shafts 19 is twice as great, for example, as the pitch of the screws on the shafts 88, then shafts 19 will move inwardly or outwardly at a rate of movement which is twice as fast as the rate of movement of the shafts 88, when the sets of shafts are operate in unison through the spiral gears 86.

In the preferred structure, the relative pitches of the screws are proportioned according to the relative differential speeding of the rolls, in order that the amount of material passed through and conveyed away from any one throat opening is proportional to the amount of material which the next set of rolls is capable of receiving.

In most conventional mills, the increase in the example, the first roll 'is driven at a relative speed of fifty, the next at a relative speed of 100 and the next at a relative speed of 200, the speed of each roll being twice the speed of the one preceding it. In such machines it is preferable to employ pitches on the lead screws which are in the same geometrical proportion. On the other hand, the pitch of the lead screws also may follow and be related to the-increase in the differential speed if it does not follow a geometrical progression.

It should here be understood that the invention is directed first to means for moving the rolls toward one another and away from one another in unison, as well as movement of the rolls toward and away from one another at predetermined relative rates which are proportioned to the diiferential speeding of the machine. The latter control concerns the principle by which the materials are being ground. The former control facilitates prompt and easy adjustment of the rolls of the machine. Each has its own virtues and advantages and the two combined cooperate to provide a grinding mill which is much easier to set up and run and, which for the most part on typical substances, gives better grinding results than if only one of the controls were employed. This brief explanation is provided in order that'those skilled in the art will understand that the present invention is not limited to either type of improvement.

Mode of operation; The mode of operation is best followed in Fig- -ures 1 and 3.

. dependent upon the direction of rotation of the hand wheel. Clockwise rotation of the hand wheel, for example, causes the leads l9 and 88 to move outwardly. This relieves the pressure on the clevis arms '28, the connecting screws .95 and 96 relieve the pressure upon the compression pins, and therefore-the journals, and the journals follow the'connecting screws and move in outward directions under the influence of the compression springs 33 and 34. Counterclock-.

wise movement of the hand wheels Bland 62a causes reverse movement of the parts and the journals are moved to bring the rolls together.

The screws 95 and 96 serve the purpose of transferring the motion of the clevis arms through the compression pins to the journals, but these screws also provide for independent adjustment of the respective journals. The independent adjustments are requisite from the practical point of view. .They provide the means for aligning the rolls to parallel condition when the machine is first erected, or for reassembly of the machine after the rolls have been reground, having. become worn through usage. They also provide adjustments for the rolls in case the frame of the machine has been sprung slightly, as for instance, by a foreign material differential speeding from one set of rolls to being passed through the machine inadvertently.

The threads of when the rolls are to be fed so that the throat portional to the relative diflerential speeding o1 the mils, then the adjustment is made as'iollows:

The hand wheel 62 is turnedin'a clockwise direction so that the rolls are moved away from one another, say, live to. ten thousandths of an inch. Next, by means of feeler gauges the throat opening between the feed roll and the middle rollis set to a given value, say, eight thousandths of an inch, by adjusting the compensating screws as and as. This adjustment is made so that the feed roll is aligned with and parallel to the middle roll. Next, the apron roll is adjusted,

openings bear a predetermined relationship pro- V the rolls in series grinding relationship, with the journals at corresponding ends beinginterl connected into sets, meansfor driving the rolls Having described my invention, I claim: 1. A grinding mill which is comprised oi: a

plurality of grinding rolls having their siding in a substantially horizontal plane, irames at the opposite ends of the rolls, pairs of journals carried by the frames and rotatively carrying a't progressively increasing diflerential peripheral speeds and means for moving the Journals oi respective sets toward and away from one; an-

- other in unison while maintaining a predeterthrough the compensating screws 95 and 96', until the apron roll lies parallel to the middle roll and is spaced from it a distance determined by the relative pitch of the lead screws 19 and 80-, so that the apron roll will be in contact with the middle roll when the feed roll is pulled up into contact with the middle roll. The adjustment, therefore, is such that both the apron and feed rolls reach the middle roll at the same time when they are moved in unison.

The adjustments thus are simultaneous. Once the machine has been installed and properly adthat have been described are made so that all back lash of the gears is taken out when the rolls areibrought into grinding position.

, ed in stationary position upon the irame and other grinding rolls in a position adjacent to it but movably mounted'upon the frame for -ad-.

to the peripheral'speeding of the rolls.

minedrelationship between the relative positions of the rolls carried by the Journals such that the-widths o! the grinding spaces intermediate the rolls is inversely related to the diflerntial peripheral speeds.

2. A grinding 'mill which is comprised 01 a frame, a grinding roll which isrotatively mountjustment relative to the roll mounted instationary position upon the frame, means for adjusting the rolls independently of one another.

forobtainingparallel alignment of them, means for moving themovable rolls in unison with one another, and means for driving the rolls at progressively increasing difierential peripheral speeds, the means for moving the movable rolls in unison including adjusting screws having relatively different pitches proportioned to one another in accordance with the differential speeding of the rolls of the mill, whereby the spacing of the rolls to one another is related jinversel CHARLES R BRASINGTON; 

